Without limiting the scope of the invention, its background is described in connection with techniques and methods used to reduce signals within the Radio Frequency ("RF") range. It should be understood, however, that the principles disclosed may have application in a wide array of signal transfer systems including audio and microwave applications using bands regulated and defined by the Federal Communications Commission ("FCC").
Today a wide array of products and methods exist for transmitting and receiving broadcast audio and video signals. For example, in a typical Frequency Modulation ("FM") application, a signal generator is used to create a carrier containing the video or audio content. The carrier, in turn, is transmitted inside an envelope corresponding to the FM station's modulation frequency as prescribed by the FCC which is picked up by a receiver tuned to the modulation frequency. Similar principles are employed in other commercial RF bands such as VHF, UHF and AM.
Modern electronic design applications will often combine both digital and analog signals on a single system platform. An example is an acoustic soundboard wherein the pure acoustic waveform receives digital enhancement prior to being transferred to a rendering system such as a speaker or audio recorder. Precise engineering is required to ensure that the higher order harmonics of the fundamental base frequency are small enough to limit interference with frequencies within reserved bands such as commercial FM or AM radio.
A primary goal in digital audio processing is to make efficient use of the available signal-to-noise ratio and bandwidth over a given transmission channel. For this reason, various modulation techniques have been developed to make RF waveforms travel over long distances. Modulation refers to a way of distorting a pure waveform prior to transmission along a communications channel. The communications channel may be physical (such as copper wiring or fiber optic cabling) or air (such as radio, television or satellite).